Don responds: Mirek, that’s an excellent question. I’m afraid the answer is fairly complex. For a discussion of it, I would refer to the есть discussion in ‘Advanced Russian’ by Nakhimovsky and Leed, as well as Catherine Chvany’s article on existential ‘be.’

Among my rules of thumb are the following.

Don’t use есть when:

referring to inalienable possession, i.e. body parts, character, etc. «У меня две руки». No есть is used here because two arms are presumably a permanent attribute.